This invention relates to a pincushion distortion correction circuit suitable for use in a television receiver.
It is known in the art that top and bottom pincushion distortion of the raster on a television picture tube may be substantially eliminated by modulating the vertical rate scanning current through the deflection coils by a substantially parabolic current component at the horizontal scanning rate. Generally the desired modulation has been achieved by active circuits in which a transistor stage amplifies horizontal rate energy and has its output electrodes coupled to the vertical scanning circuit, or, by passive circuits in which a control or primary winding of a reactor or transformer is energized by horizontal rate energy and a secondary winding is placed in circuit with the vertical deflection winding. Provision must also be made to ensure that the polarity of the horizontal rate modulation reverses at the center of the vertical scanning interval and that the modulation is greatest at the beginning and end of the vertical interval and minimum at the center. Usually the circuit elements and their required interconnections result in a relatively complex and costly arrangement.